It's interesting to read the comments here and the debate around whether social media counts as a public square or not.
Ultimately, the web, and social media, is where a majority of our citizens spend a large chunk of their time. While it's certainly true, that you don't _need_ to access them to live your life, for the vast majority of us it would be more than an inconvenience to be banned.
In all other aspects of our lives, we do not accept rules imposed upon us by a large private actor. There are courts, and appeals processes, and politicians, and other channels through which we can assert our societal norms. Not so with social media today.
These societal rules and norms, are, and should be governed by a democratic process. Social media is undeniably now such a large and important part of our society and it's absurd that we do not collectively have control over the rules around it.
Other infrastructure, like trains, were also originally private endeavours where your rights are now protected by the courts, and laws of the land.
At some point, the interest of the collective takes precedence over the private rights of Zuckerberg and Dorsey. We are well past that point with social media. These private companies should be considered access points to the social graph, not owners of it, and therefore regulated as such.